I've been reading along and have meant to drop a comment, but reading your posts from the last few days, I am feeling I can relate to you even more. If nothing else I say sticks, at least take away that you should try to stay away from H's FB! That has been the beginning of my undoing over the last couple of weeks as well. I know it's hard, but you have to try (as I continue to "try" to take my own advice).
Regarding this person, I would stay far away from her. It's clear she couldn't care less about you or your feelings. If she did, she wouldn't be sharing the great time they are having at all of the parties you are no longer invited to because he left you. Anybody with an ounce of empathy in their body would realize that and zip it. And as job said, she has no clue what she's talking about. Lots of great advice from someone who has not even walked 1 step your shoes.
When you wrote that the the more you hear about H, the less you like him and the easier it is to never want to see him again, hit home for me. I had seen a recent pic of H and he didn't look great. Not horrible, just sloppy and not normally as good looking and OW was in pic so even worse, but I got a little grossed out by him. That has always helped me in prior Rs, the minute I'm really grossed out by them, I am able to pull away. Ha! I know, this is my H, not just a boyfriend and many more years of history, so that's going to be a bit harder to achieve. My point is that I think once H has done enough damagae to erase our prior memories of who they were, it might begin to help in the letting go.
You said it best, you and D have been doing just fine w/out him (& his weird friends) and you will continue on that path w/ or w/out him. I have faith you and know you'll make through to the other side like a champ!
M:43 H:44 M:10 T:14 S:26 BD:7/21/17 H files for D:7/31/17 (haven't been served) PA:8/30/17
